An ultra-stable controller for scanning of magnetic field over 1000 G range was developed on the basis of UTRASTUB (GMW) current sensor and TECHRON 7570 power amplifier. The system is designed for a resistive coil insert accessory to add fine sweep capability to a superconductive magnet. It is optimized for both the Oxford and Illinois design water-cooled sweep coil in the Mark II superconducting W-band magnet system at IERC. It has a stability better then 30 ppm. relative to the sweep field. The system was put into regular operation during the previous project year and was further tested and refined during 1995. The controller can operate in both manual and computer controlled modes.